Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 182349
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
649 PM CDT FRI JUL 18 2014

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 345 PM CDT FRI JUL 18 2014

THINGS LOOK TO REMAIN REASONABLY QUIET THROUGH THE SHORT TERM...
ALTHOUGH WE WILL FINALLY BE BRINGING MOISTURE AND INSTABILITY INTO
THE REGION... SO IT WILL LIKELY BE THE LAST SUCH SHORT TERM PERIOD.
LATEST VISIBLE IMAGERY SHOWS SCATTERED CU ACROSS THE AREA ONCE
AGAIN TODAY... UNDER A CANOPY OF LINGERING SMOKE AND SOME SCATTERED
AC. SURFACE ANALYSIS SHOWS A COLD FRONT OVER THE NORTHERN PLAINS...
AND THIS FEATURE WILL TRY TO COME AT US LATE TONIGHT AND SATURDAY...
BUT WILL MISERABLY FAIL IN THAT ATTEMPT. SHRA/TSRA SHOULD DEVELOP
ALONG/AHEAD OF THE FRONT THIS AFTERNOON/EVENING WHERE THERE IS A
NICE RIBBON OF 1000-2000 J/KG MLCAPE AND DECENT FORCING ASSOCIATED
WITH A SHORTWAVE NORTH OF THE CANADIAN BORDER, A SECOND FEATURE CAN
BE SEEN MOVING THROUGH SOUTH DAKOTA AT THE CURRENT TIME... BUT IT
APPEARS THAT IT WILL OUTPACE THE LOW LEVEL FORCING AND
INSTABILITY... AND SHOULDN/T DO MUCH IF ANYTHING AS A RESULT.
HOWEVER... STORMS WHICH DO FORM OVER THE DAKOTAS WILL TRACK EAST AND
ATTEMPT TO WORK INTO OUR AREA OVERNIGHT TONIGHT. BUT... GIVEN THE
DRY AIR CURRENTLY IN PLACE AND CAPPING EVIDENT ON OUR 12Z
SOUNDING... THIS INITIAL ATTEMPT SHOULD LARGELY FAIL AND MAINLY JUST
SERVE TO REDUCE THAT CAP A BIT WHILE MOISTENING UP THE PROFILE SOME.
DID BRING SOME CHANCE POPS INTO THE FAR WEST/NORTHWEST TONIGHT...
BUT DRIED THEM OUT QUICKLY AS THEY TRY TO SHIFT EAST. THE CAM
SOLUTIONS... INCLUDING THE HOPWRF... SPCNMM... AND HIRES WINDOWS...
ALL SHOW A SIMILAR WEAKENING EVOLUTION WITH THIS ACTIVITY AS WELL.
ON SATURDAY... WHAT/S LEFT OF THE COLD FRONT WILL MOVE ACROSS THE
AREA... BUT BY LATE IN THE DAY THERE WILL BE LITTLE TO NO BAROCLINIC
OR FORCING ASSOCIATED WITH IT. SOME KINEMATIC FORCING FROM A
LINGERING WIND SHIFT WILL REMAIN... AND THAT COULD BE SUFFICIENT
TO KICK OFF ISOLATED/SCATTERED SHRA/TSRA OVER THE CENTRAL AND
EASTERN PART OF THE AREA BY LATER SATURDAY AFTERNOON INTO SATURDAY
EVENING. SO... ALLOWED FOR SOME POPS TO REDEVELOP ACROSS THAT
PORTION OF THE AREA DURING THE AFTERNOON.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY) ISSUED AT 345 PM
CDT FRI JUL 18 2014

HOT AND HUMID CONDITIONS WILL DEVELOP ACROSS THE MIDWEST AS AN UPPER
LEVEL RIDGE BUILDS OVER THE 4 CORNERS REGION. DIABATIC HEATING
ALONG THE FOOTHILLS OF THE ROCKIES WILL DEVELOP A SEASONABLY HOT
AIRMASS...AND THIS AIRMASS WILL OVERSPREAD THE UPPER MIDWEST. H850
TEMPERATURES OF 20 TO 25C WILL SUPPORT SURFACE TEMPERATURES IN THE
LOW TO MID 90S ACROSS THE DAKOTAS AND WESTERN MN SUNDAY. THIS HEAT
WILL SHIFT EASTWARD ON MONDAY...AS DEWPOINTS CLIMB INTO THE MID 70S.
AS ALLUDED TO IN THE PREVIOUS FORECAST DISCUSSION...CONVECTIVE
DEBRIS WILL BE THE LIMITING FACTOR ON TEMPERATURES...BUT AS OF NOW
EXPECT HEAT INDICES IN MN TO BE IN THE 100 TO 110F RANGE BY MID
AFTERNOON.

SPEAKING OF CONVECTION...CONFIDENCE IS LOW IN ANY PRECIP BEFORE
MONDAY EVENING. THE MLCAPE MAX OFF THE GFS/NAM IS CENTERED ACROSS
MN/WI...WHICH IMPLIES THAT THE REGION WILL BE CAPPED OFF IN ORDER TO
GENERATE THAT AMOUNT OF INSTABILITY. FORECAST SOUNDINGS SUPPORT THIS
HYPOTHESIS. IN ADDITION...THERE IS ACTUALLY LOW LEVEL DIVERGENCE AT
H850...SO DESPITE THE THETA_E ADVECTION AND 30-40KT LOW LEVEL JET
FEEL THAT THE CAP WILL HOLD AND MOST OF THE CWA WILL STAY DRY.

BY MONDAY NIGHT ALL THE NUMERICAL MODELS BRING A SHORTWAVE CURRENTLY
LOCATED OFF THE SOUTHERN CALIFORNIA SHORE OVER THE 500MB RIDGE AND
ACROSS THE UPPER MIDWEST. GIVEN THE THERMODYNAMICALLY RICH
ENVIRONMENT CHARACTERIZED BY 4000-5000J/KG OF MUCAPE...AND PWATS
IN EXCESS OF 2IN...THE NUMERICAL MODELS VIGOROUSLY DEVELOP PRECIP
THROUGH THE DAY ON TUESDAY. THERE APPEARS TO BE SOME CONVECTIVE
FEEDBACK WITH THIS SYSTEM...AND AT THIS TIME FEEL THE HIGHEST
CHANCE FOR PRECIP WILL BE NORTH OF I94 TIED TO THE UPPER LEVEL
FORCING. IF STORMS DO MANAGE TO DEVELOP THEY COULD PROPAGATE
SOUTHEASTWARD. THE HIGHEST RISK APPEARS TO BE HEAVY RAIN SINCE
BOTH MEAN WIND AND SHEAR WILL BE LIGHT WITHIN THE COLUMN. LOOKING
AHEAD...COOLER AND DRIER AIR WILL BRING MORE SEASONABLE CONDITIONS
FOR THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 649 PM CDT FRI JUL 18 2014

QUIET EVENING WITH JUST SOME CU AND A LITTLE BIT OF BROKEN AC.
SSW WINDS GENERALLY 10-15 KTS WITH SOME HIGHER GUSTS AND THE WIND WILL
TAKE A LITTLE TIME TO DROP OFF SINCE GRADIENT REMAINS MUCH OF THE
NIGHT. INCOMING COLD FRONT WEAKENS AND THERE IS QUITE A BIT OF INDICATION
IN VARIOUS MODELS THAT IT WILL NOT EVEN MAKE IT TO EAST CENTRAL
OR SW MN MUCH LESS WISCONSIN. SOME SHRA/TSRA COULD MAKE IT INTO
WEST CENTRAL MN AND HAVE CONTINUED THE MENTION OF THUNDER LATE TONIGHT
FOR KAXN. REST OF AREA WILL JUST SEE OCCASIONAL BROKEN MID
CLOUDS.

KMSP...WITH FRONT REMAINING TO THE NORTHWEST SATURDAY...ANTICIPATE ONLY
SOME BROKEN MID CLOUDS TOMORROW FROM LEFTOVER SHOWERS THAT
DISSIPATE WELL TO THE NORTHWEST. OTHERWISE JUST SOME SCATTERED CU
AND MID CLODUS TONIGHT. THERE WILL BE SOME GUSTS AROUND 20 KNOTS
THIS EVENING BUT THEY ARE EXPECTED TO WEAKEN WITH SUNSET. GRADIENT
SHOULD KEEP SUSTAINED SOUTH WINDS AROUND 8-10 KNOTS OVERNIGHT...
THEN MORE GUSTS CLOSE TO 20 KNOTS ON SATURDAY AS GRADIENT REMAINS
PARKED OVER THE AREA.

/OUTLOOK FOR KMSP/
SUNDAY...VFR. SOUTH WIND 10-15 KTS WITH GUSTS TO 20 KTS.
MONDAY...VFR. SOUTH WIND 10 KTS.
TUESDAY...MVFR POSSIBLE WITH A CHANCE OF SHRA/TSRA. SOUTH WIND 5
TO 15 KT BECOMING WEST TUESDAY AFTERNOON.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

SHORT TERM...
LONG TERM...JRB
AVIATION...TDK






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